Response of four apple cultivars to 1-methylcyclopropene treatment and controlled atmosphere storage

Abstract

Apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf. ('Gala', 'Delicious', 'Granny Smith' and 'Fuji')], pretreated or nontreated with 1-methylcyclopropene (1-MCP, 0.6 to 1.0 μL·L-1 for 18 hours at 20°C), were stored in controlled atmosphere (CA, 1 to 1.5 kPa O 2; 1 to 2 kPa CO2) or in regular atmosphere (RA) for up to 8 months at 1°C. Firmness, titratable acidity (TA), soluble solids content (SSC), and volatile abundance were analyzed every month directly or after transfer to air at 20°C for 1 week to determine effect of 1-MCP, storage atmosphere and storage time on apple quality immediately after cold storage and after simulated marketing conditions at 20°C. The 1-MCP ± CA treatments delayed ripening and prolonged storage life as indicated by delayed loss of firmness and TA in all four cultivars during storage. The 1-MCP ± CA also slightly delayed loss of SSC for 'Gala' but had no effect on SSC levels for the other cultivars. There were differences among treatments for firmness and TA content [(1-MCP + RA) > CA] for 'Gala', 'Delicious', and 'Granny Smith' apples, but not for 'Fuji'. These differences were generally exacerbated after transfer of fruit to 20°C for 1 week. A combination of 1-MCP + CA was generally best [(1-MCP + CA) > (1-MCP + RA) or CA] for maintaining 'Delicious' firmness and TA. However, the treatments that were most effective at retaining TA and firmness also retained the least volatiles. The results indicate that the efficacy of 1-MCP and CA in maintaining apple quality factors is cultivar dependent and that 1-MCP + RA may be a viable alternative to CA for optimal eating quality for some cultivars.